Seven were arrested after they bought drugs from undercover officers, police said. The others were arrested on warrants that had been issued in connection with crimes committed over the last three months.

Police on Thursday night were still looking for at least eight more people wanted on drug charges.

Undercover officers began working the park in January after the department received complaints of drug use.

"Word got out that you can buy your drug of choice in Williams Park," said Assistant Police Chief Dave DeKay. "They shouldn't feel comfortable breaking the law in a city park."

Last month, a Tampa Bay Times story illustrated how the area has become an oasis of illegal activity. Soon after, City Council members vowed to once again make it a safe, welcoming space for families and downtown professionals.

Almost immediately, city officials increased an already consistent police presence.

Mayor Bill Foster pushed a plan to ban the park's most prevalent drug — synthetic marijuana known as "spice" — from stores. Officials also visited downtown grocery marts to pass out fliers asking clerks to stop selling the drug.

"Spice has been the number one issue, the drug of choice, because it's legal," Foster said Thursday. "It makes people crazy."

Foster said he and other city leaders will meet in the coming weeks with representatives from St. Petersburg College to discuss student activities that could be held in the park. He also hopes to lure food trucks along Third Street N.

The city will soon begin experimenting with brick designs that make it more difficult for people to lounge along the bordering walls.

The Pinellas Suncoast Transit Authority, which manages the park's 16 bus routes, already has removed windows that had enclosed the shelters. The change should help police better monitor what's happening inside and discourage the surreptitious illegal activity for which they've become known. PSTA also will install better lighting at the shelters.

Still, many city leaders believe the buses must be removed for the park's long-term recovery.

It remains unclear which of these efforts, if any, will create substantial change.

Midday Friday, before many of the arrests, the park looked much like it did a month ago.

The air smelled of spice. Bottles passed from hand to hand. Two men threatened each other until their disagreement erupted into a fist fight. At least three people were charged with disorderly conduct.

The police hope Thursday's sweep will make a difference.

The 19 people arrested were charged with crimes related to nine different drugs. They were: cocaine, crack cocaine, methadone, morphine, hydromorphone, suboxone, heroin, oxycodone and marijuana.

Times staff writer Meredith Rutland contributed to this report. John Woodrow Cox can be reached at jcox@tampabay.com.